Csst Astrometry Predicts Detection of Giant Planets and Brown Dwarfs with Yields of Hundreds

The search for planets beyond our solar system receives a significant boost from upcoming astronomical surveys, and a new study predicts the potential of China’s planned Chinese Space Station Telescope (CSST) to discover previously hidden giant planets and brown dwarfs. Yifan Xuan, Fabo Feng, and colleagues from the Tsung-Dao Lee Institute, alongside Shilong Liao from the Shanghai Astronomical Observatory and others, demonstrate that CSST’s high-precision astrometry, measuring the precise positions of stars, will be particularly effective at identifying these objects orbiting M-dwarfs and brown dwarfs. The team simulated the CSST’s observations, revealing it could detect between 20 and 170 giant planets and low-mass brown dwarfs around M-dwarfs within a 300 light-year radius, and 300 to 570 brown dwarf binaries within 600 light-years. This projected yield promises to substantially expand the known population of substellar companions, offering crucial insights into the formation and evolution of planetary systems around low-mass stars and brown dwarfs.

This ambitious project aims to achieve high astrometric precision, particularly for faint objects, utilising the CSST Survey Camera. The telescope’s design prioritises detailed observations across a significant portion of the celestial sphere, enabling a comprehensive study of stellar populations and galactic structure. This survey will provide a valuable dataset for a wide range of astronomical investigations, furthering our understanding of the universe.

Binary Star Orbit Analysis and Data

Scientists are analysing data from numerous publications to prepare for future observations. These studies cover a range of topics, including stellar populations, binary star systems, and exoplanet detection techniques. Research from 2004 by Padoan and Nordlund, and work by Reipurth and Clarke in 2001, contribute to the understanding of star formation processes. Muterspaugh and colleagues, in a 2010 study, detailed observations of binary stars, while Stumpf and others, also in 2010, investigated similar systems. Further research by Wright and Howard in 2009, and Sozzetti in 2023, expands on these findings.

Recent investigations by Ment and Charbonneau, and Pass and colleagues, both in 2023, focus on substellar objects and their characteristics. Martín and co-authors, in a 2024 publication, present new data on brown dwarf atmospheres, and Lu and Chen, also in 2024, explore stellar populations. Pan and others, in 2024, investigate planetary systems, while Mignon and colleagues, in 2025, present findings on exoplanet detection. This research predicts the number of these substellar companions detectable through precise measurements of their orbital motions, a technique called differential astrometry. Scientists generated detailed simulations of the stars and brown dwarfs CSST will observe, modelling a vast population of celestial objects to test the telescope’s capabilities. These simulations incorporated realistic models of stellar populations, including the distribution of FGK-dwarfs, M-dwarfs, and brown dwarfs within 300 and 600 parsecs of Earth.

Experiments reveal that while detecting giant planets around FGK-dwarfs will prove challenging for CSST, the telescope is projected to identify between 20 and 170 giant planets and low-mass brown dwarfs orbiting M-dwarfs within a 300 parsec radius. Furthermore, the study forecasts the discovery of 300 to 570 brown dwarf binary systems within 600 parsecs. The synthetic stellar catalogue comprises 1.52x 10 5 FGK-dwarfs and 1.15x 10 6 M-dwarfs, closely aligning with the numbers observed by the Gaia mission within similar distances.

The team constructed a mock catalogue of substellar objects using initial mass functions derived from observations of star and brown dwarf populations, extending the mass range down to the planetary regime. This work demonstrates that CSST astrometry will substantially increase the known population of substellar companions around M-dwarfs and brown dwarfs, providing a rich dataset to investigate the processes of planet formation and evolution in these low-mass stellar systems. Through detailed simulations of CSST’s capabilities, scientists estimate the telescope will detect between 83 and 170 giant planets and low-mass brown dwarfs around M-dwarfs within a 300 parsec radius, and between 420 and 570 brown dwarf binaries within 600 parsec during its ten-year mission. This contrasts with limited detection potential around brighter FGK-dwarfs, highlighting CSST’s strength in observing fainter, lower-mass stars. Future research could further enhance CSST’s capabilities through dedicated observing proposals focusing on smaller sky areas with increased cadence, potentially achieving Gaia-level precision and enabling the detection of smaller planets with shorter orbital periods, and combining CSST data with existing Gaia observations to identify companions with longer orbital periods. The team notes that the number of detectable companions is influenced by factors such as the age of the brown dwarf and the orbital inclination of the system, with younger systems and face-on orientations being easier to detect.